Highly filled polyvinyl chloride (PVC) is commonly used in forming PVC floor tiles and rolled flooring with very high levels of filler, often in the 75-90 weight percentage range. High levels of filler are also used in PVC composites used in pipe and siding, window and door components, fencing and other architectural components—though the levels of filler are much lower than in the flooring applications. High levels of filler are used to reduce costs, and a minimal amount of polyvinyl chloride is used to hold the filler together. The processing of these highly filled flooring composites can be difficult, and often requires expensive vinyl copolymers, such as a polyvinyl alcohol (PVA)/PVC copolymer.
U.S. Pat. No. 5,084,501 describes a highly filled PVC resin powder (60 to 95% filler) in which the filler particles are coated prior to blending with the PVC resin.
Acrylic copolymer process aids that are 80 weight percent methylmethacrylate units and 20 weight percent butyl acrylate have been use as process aids for highly filled PVC siding.
Surprisingly, it has now been found that acrylic copolymers having 80 weight percent or less of methyl methacrylate units, and lower Tgs work extremely well as process aids for highly filled PVC composites. The PVC/CPVC composites of the invention show a faster fusion, and a lower time to band.